1. Field of the Invention
This invention relates to novel phosphate esters prepared from polycyclic phosphorohalidites. These esters, which are useful as flame retardants especially for rigid polyurethane foams, have the formula: RO[(A).sub.m (B).sub.n ]H wherein A has the structural formula ##STR3## and B has the structural formula ##STR4## wherein R, R.sup.1, and R.sup.2 are the same or different and are alkyl radicals, and m and n are integers from 0 to about 4, the sum of m plus n being from one to about four. It is understood that structures A and B are randonmly distributed within these oligomeric compounds.